This invention relates to the general category of devices employing "neural networks." As disclosed in U.S. Pat. No. 5,136,687, Ser. No. 419,524, filed Oct. 10, 1989, entitled "Categorization Automata Employing Neuronal Group Selection With Reentry" and assigned to the same assignee, such devices are capable of learning and of discriminating and selecting objects based upon characteristics that are not predetermined when the device is designed or constructed. The complete disclosure of that application is incorporated herein by references and generally teaches how to construct a selection and discrimination automaton or robot incorporating a neural network of a particular kind. Such networks are made up of a number of interconnected units, often called "cells;" the connections between cells are often called "synapses." This terminology is based on an analogy to biological systems. Each cell usually has several (or many) inputs from other cells in the network, and in some way it integrates these inputs to determine its (usually) single-valued output, which is then transmitted via synapses to other cells. Typically, each synapse has an associated mathematical "weight" that determines the relative influence of that particular synapse in the cellular integration. In each "cycle" of the device, these synaptic weights may be changed to alter the behavior of the overall network. There have been many such networks developed for different purposes in the past few years. While these network schemes differ in significant detail, they share the common feature that rules for changing the synaptic weights depend only on the previous or current activity of the cell and its connections, perhaps including some parameters that decay with time, and perhaps on the overall current performance level of the network, e.g., the difference between an expected output and the observed output.
In these various systems, there is no direct way for a cell to influence the behavior of those cells to which it is not connected. Useful synaptic modification rules are thus constrained. Furthermore, connections between units are usually established at the outset, and there is no mechanism for making new connections or removing old ones (other than by setting their weights to zero) as the device operates.